1. Field of The Invention
This invention relates to aqueous surfactant solutions containing special thickeners.
Aqueous surfactant solutions, particularly those used in the field of body care as shampoos, bubble baths, shower baths, hand washing pastes and the like, generally contain anionic surfactants such as alkyl ether sulfates, for example, as surfactant components. To stabilize these clear or disperse surfactant solutions and to improve their handling properties, thickeners are normally added.
Several inorganic and organic compounds which are used to increase the viscosity of aqueous solutions containing anionic surfactants are already known to the expert.
A number of water-soluble salts, such as sodium chloride for example, may be used as inorganic thickeners. Organic thickeners include, inter alia, fatty acid alkanolamides such as coconut oil fatty acid monoethanolamide, lauric acid monoethanolamide, oleic acid diethanolamide and coconut oil fatty acid diethanolamide, polyethylene glycol difatty acid esters and a number of water-soluble polymers.
Where inorganic salts alone are used, the desired viscosity in the surfactant solution can in general only be built up, if at all, by using high concentrations. Accordingly, it is normally necessary to use the inorganic salts in conjunction with organic thickeners which are attended by a number of disadvantages. For example, the solutions thickened with polyethylene glycol fatty acid diesters often show inadequate viscosity stability in storage while water-soluble polymers are often poorly soluble and produce unwanted, slimy flow behavior with a tendency towards "stringing". Fatty acid alkanolamides are becoming increasingly undesirable in cosmetic preparations because a small production-induced content of free alkanolamines can give rise to nitrosamine formation.
2. Discussion of Related Art
Accordingly, it has been proposed in German patent application P 37 30 179.9 to use adducts of ethylene oxide and/or propylene oxide with unsaturated fatty alcohols to thicken surfactant solutions. These products are not attended by the disadvantages mentioned above. However, there is a need for thickeners which have an increased thickening effect for comparable properties. For a given thickener content, this would facilitate the production of systems having relatively high viscosity and reduction of the thickener content for a given viscosity.